Network Working Group Dayong Guo
Internet Draft Sheng Jiang (Editor)
Intended status: Standards Track Huawei Technologies Co., Ltd
Expires: February 20, 2012 R. Despres
RD-IPtech
R. Maglione
Telecom Italia
August 19, 2011
RADIUS Attribute for 6rd
draft-ietf-softwire-6rd-radius-attrib-03.txt
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Abstract
IPv6 Rapid Deployment (6rd) is one of the most popular methods to
provide both IPv4 and IPv6 connectivity services simultaneously
during the IPv4/IPv6 co-existing period. The Dynamic Host
Configuration Protocol (DHCP) 6rd option has been defined to
configure 6rd Customer Edge (CE). However, in many networks, the
configuration information may be stored in Authentication
Authorization and Accounting (AAA) servers while user configuration
is mainly from Broadband Network Gateway (BNG) through DHC protocol.
This document defines a Remote Authentication Dial In User Service
(RADIUS) attribute that carries 6rd configuration information from
AAA server to BNG.
Table of Contents
1. Introduction ................................................ 3
2. Terminology ................................................. 3
3. IPv6 6rd Configuration with RADIUS .......................... 3
4. Attributes .................................................. 5
4.1. IPv6-6rd-Configuration Attribute ....................... 5
4.2. Table of attributes .................................... 8
5. Diameter Considerations ..................................... 8
6. Security Considerations ..................................... 8
7. IANA Considerations ......................................... 9
8. Acknowledgments ............................................. 9
9. Change Log [RFC Editor please remove] ....................... 9
10. References ................................................. 9
10.1. Normative References .................................. 9
10.2. Informative References ............................... 10
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1. Introduction
Recently providers start to deploy IPv6 and consider how to transit
to IPv6. IPv6 Rapid Deployment (6rd) [RFC5969] is one of the most
popular methods to provide both IPv4 and IPv6 connectivity services
simultaneously during the IPv4/IPv6 co-existing period. 6rd is used
to provide IPv6 connectivity service through legacy IPv4-only
infrastructure. 6rd adopt Dynamic Host Configuration Protocol (DHCP)
as auto-configuring protocol. The 6rd Customer Edge (CE) extends DHCP
option to discover 6rd border relay and to configure IPv6 prefix and
address.
In many networks, user configuration information may be managed by
AAA servers, together with user Authentication, Authorization, and
Accounting (AAA). Current AAA servers communicate using the Remote
Authentication Dial In User Service (RADIUS) [RFC2865] protocol.
In a fixed line broadband network, the Broadband Network Gateways
(BNGs) act as the access gateway of users. The BNGs are assumed to
embed a DHCP server function that allows them to locally handle any
DHCP requests issued by hosts.
Since the 6rd configuration information is stored in AAA servers and
user configuration is mainly through DHC protocol between BNGs and
hosts. New RADIUS attributes are needed to propagate the information
from AAA servers to BNGs.
2. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC2119 [RFC2119].
The terms 6rd CE and 6rd Border Relay are defined in [RFC5969].
3. IPv6 6rd Configuration with RADIUS
The below Figure 1 illustrates how the RADIUS protocol and DHCP
cooperate to provide 6rd CE with 6rd configuration information.
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6rd CE BNG AAA Server
| | |
|-------DHCPDISCOVER------>| |
| |--Access-Request(6rd Attr)-->|
| | |
| |<--Access-Accept(6rd Attr)---|
|<-------DHCPOFFER---------| |
| | |
|--------DHCPREQUEST------>| |
| (6rd Option) | |
|<--------DHCPACK----------| |
| (6rd option) | |
| | |
DHCP RADIUS
Figure 1: the cooperation between DHCP and RADIUS
BNGs act as a client of RADIUS and as a DHCP server for DHC protocol.
First, a BNG receives a DHCPDISCOVER from the 6rd CE. It initiates
the BNG to request correspondent user authentication relevant from an
AAA server using RADIUS protocol. A 6rd configuration request may be
also sent in the same message. If the user authentication is approved
by the AAA server, an Access-Accept message is acknowledged with the
IPv6-6rd-Configuration Attribute, defined in the next Section. After
the BNG responds to the user with an Advertise
message, the user requests for a 6rd Option. Then, the BNG can reply
the user using DHCP protocol.
Figure 2 describes another scenario, in which the authentication
operation is not coupled with DHCP. In the authentication stage, the
BNG obtains the 6rd configuration information from the AAA server
through RADIUS protocol. When the user requests the 6rd Option, the
BNG replies with a 6rd option in DHCPACK.
6rd CE BNG AAA Server
| | |
| |--Access-Request(6rd Attr)-->|
| | |
| |<--Access-Accept(6rd Attr)---|
| | |
|--------DHCPREQUEST------>| |
| (6rd Option) | |
|<---------DHCPACK---------| |
| (6rd option) | |
| | |
DHCP RADIUS
Figure 2: the cooperation between DHCP and RADIUS
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After receiving the IPv6-6rd-Configuration Attribute in the initial
Access-Accept, the BNG MUST store the received 6rd configuration
parameters locally. When the 6rd Customer Edge sends a DHCP Request
message to request an extension of the lifetimes for the assigned
address, the BNG does not have to initiate a new Access-Request
towards the AAA server to request the 6rd configuration parameters.
The BNG retrieves the previously stored 6rd configuration parameters
and use them in its reply.
If the DHCP server to which the DHCP Request message was sent at time
T1 has not responded, the DHCP client enters the REBINDING state and
attempts to contact any server. In this scenario the BNG receiving
the DHCP message MUST initiate a new Access-Request towards the AAA
server. The BNG MAY include the IPv6-6rd-Configuration Attribute in
its Access-Request. If the BNG does not receive the IPv6-6rd-
Configuration Attribute in the Access-Accept it MAY fallback to a
pre-configured default 6rd configuration, if any. If the BNG does not
have any pre-configured default 6rd configuration or if the BNG
receives an Access-Reject, the tunnel cannot be established.
4. Attributes
This section defines IPv6-6rd-Configuration Attribute which is used
in the 6rd scenario. The attribute design follows [RFC6158].
4.1. IPv6-6rd-Configuration Attribute
The IPv6-6rd-Configuration Attribute is structured as follows (The
specification requires that multiple IPv4 addresses are associated
strongly with one IPv6 prefix. Given that RADIUS currently has no
recommended way of grouping multiple attributes, the below design
appears to be a reasonable compromise.):
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0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length | SubType | SubLen |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv4MaskLen | SubType | SubLen | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 6rdPrefixLen | |
+-+-+-+-+-+-+-+-+ +
| |
+ +
| 6rdPrefix |
+ +
| |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | SubType | SubLen |6rdBRIPv4Address|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 6rdBRIPv4Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type
TBD
Length
25 + n*6 (the length of the entire attribute in octets; n
stands the number of BR IPv4 addresses, minimum n is 1).
SubType
1 (SubType number, for the IPv4 Mask Length suboption)
SubLen
3 (the length of the IPv4 Mask Length suboption)
IPv4MaskLen
The number of high-order bits that are identical across all CE
IPv4 addresses within a given 6rd domain. This may be any value
between 0 and 32. Any value greater than 32 is invalid.
SubType
2 (SubType number, for the 6rd prefix suboption)
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SubLen
20 (the length of the 6rd prefix suboption)
Reserved
Set to be all 0 for now. Reserved for the future use. To be
compatible with other IPv6 prefix attributes in the Radius
Protocol.
6rdPrefixLen
The IPv6 Prefix length of the Service Provider's 6rd IPv6
prefix in number of bits. The 6rdPrefixLen MUST be less than or
equal to 128.
6rdPrefix
The Service Provider's 6rd IPv6 prefix represented as a 16
octet IPv6 address. The bits after the 6rdPrefixlen number of
bits in the prefix SHOULD be set to zero.
SubType
3 (SubType number, for the 6rd Border Relay IPv4 address
suboption)
SubLen
6 (the length of the 6rd Border Relay IPv4 address suboption)
6rdBRIPv4Address
One or more IPv4 addresses of the 6rd Border Relay(s) for a
given 6rd domain. The maximum RADIUS Attribute length of 255
octets results in a limit of 58 IPv4 addresses.
The IPv6-6rd-Configuration Attribute MAY be used in Access-Request
packets as a hint to the RADIUS server; for example if the BNG is
pre-configured with a default 6rd configuration, these parameters MAY
be inserted in the attribute. The RADIUS server MAY ignore the hint
sent by the BNG and it MAY assign different 6rd parameters.
If the BNG includes the IPv6-6rd-Configuration Attribute, but the AAA
server does not recognize it, this attribute MUST be ignored by the
AAA Server.
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If the BNG does not receive IPv6-6rd-Configuration Attribute in the
Access-Accept it MAY fallback to a pre-configured default 6rd
configuration, if any. If the BNG does not have any pre-configured
default 6rd configuration, the 6rd tunnel can not be established.
If the BNG is pre-provisioned with a default 6rd configuration and
the 6rd configuration received in Access-Accept is different from the
configured default, then the 6rd configuration received in the
Access-Accept message MUST be used for the session.
If the BNG cannot support the received 6rd configuration for any
reason, the tunnel SHOULD NOT be established.
4.2. Table of attributes
The following table provides a guide to which attributes may be found
in which kinds of packets, and in what quantity.
Request Accept Reject Challenge Accounting # Attribute
Request
0-1 0-1 0 0 0-1 TBD IPv6-6rd-
Configuration
The following table defines the meaning of the above table entries.
0 This attribute MUST NOT be present in packet.
0+ Zero or more instances of this attribute MAY be present in
packet.
0-1 Zero or one instance of this attribute MAY be present in
packet.
1 Exactly one instance of this attribute MUST be present in
packet.
5. Diameter Considerations
This attribute is usable within either RADIUS or Diameter [RFC3588].
Since the Attributes defined in this document will be allocated from
the standard RADIUS type space, no special handling is required by
Diameter entities.
6. Security Considerations
In 6rd scenarios, the RADIUS protocol is run over IPv4. Known
security vulnerabilities of the RADIUS protocol are discussed in RFC
2607 [RFC2607], RFC 2865 [RFC2865], and RFC 2869 [RFC2869]. Use of
IPsec [RFC4301] for providing security when RADIUS is carried in IPv6
is discussed in RFC 3162 [RFC3162].
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Security considerations for the Diameter protocol are discussed in
RFC 3588 [RFC3588].
7. IANA Considerations
This document requires the assignment of one new RADIUS Attribute
Types in the "Radius Types" registry (currently located at
http://www.iana.org/assignments/radius-types for the following
attributes:
o IPv6-6rd-Configuration
IANA should allocate the number from the standard RADIUS Attributes
space using the "IETF Review" policy [RFC5226].
8. Acknowledgments
The authors would like to thank Maglione Roberta, Alan DeKok, for
valuable comments.
9. Change Log [RFC Editor please remove]
draft-ietf-softwire-6rd-radius-attrib-03, add attribute operation
procedures according to IESG review comments for draft-ietf-softwire-
dslite-radius-ext, 2011-08-19.
draft-ietf-softwire-6rd-radius-attrib-02, redesign the sub TLVs of
the attribute according to Radext WG reviewing, 2011-04-20.
draft-ietf-softwire-6rd-radius-attrib-01, minor modifications after
Radext WG reviewing, 2010-11-22.
draft-ietf-softwire-6rd-radius-attrib-00, accept as Softwire WG draft
in IETF 79, 2010-11-15.
draft-guo-softwire-6rd-radius-attrib-00, renaming and deleting DS-
lite contents, 2010-10-18.
draft-guo-radext-softwire-concentrator-00, original version, 2010-07-
05.
10. References
10.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
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[RFC2865] Rigney, C., Willens, S., Rubens, A., and W. Simpson,
"Remote Authentication Dial In User Service (RADIUS)", RFC
2865, June 2000.
[RFC3162] Aboba, B., Zorn, G., and D. Mitton, "RADIUS and IPv6", RFC
3162, August 2001.
[RFC3588] Calhoun, P., Loughney, J., Guttman, E., Zorn, G., and J.,
Arkko, "Diameter Base Protocol", RFC 3588, September 2003.
[RFC4301] Kent, S. and K. Seo, "Security Architecture for the
Internet Protocol", RFC 4301, December 2005.
[RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", RFC 5226, May 2008.
[RFC5969] Townsley, M. and O. Troan, "IPv6 Rapid Deployment on IPv4
Infrastructures (6rd) -- Protocol Specification", RFC5969,
August 2010.
[RFC6158] DeKok, A. and G. Weber, "RADIUS Design Guidelines", RFC
6158, March 2011.
10.2. Informative References
[RFC2607] Aboba, B. and J. Vollbrecht, "Proxy Chaining and Policy
Implementation in Roaming", RFC 2607, June 1999.
[RFC2869] Rigney, C., Willats, W., and P. Calhoun, "RADIUS
Extensions", RFC 2869, June 2000.
Author's Addresses
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Dayong Guo
Huawei Technologies Co., Ltd
Huawei Building, No.3 Xinxi Rd.,
Shang-Di Information Industry Base, Hai-Dian District, Beijing 100085
P.R. China
Email: guoseu@huawei.com
Sheng Jiang (Editor)
Huawei Technologies Co., Ltd
Huawei Building, No.3 Xinxi Rd.,
Shang-Di Information Industry Base, Hai-Dian District, Beijing 100085
P.R. China
Email: jiangsheng@huawei.com
Remi Despres
RD-IPtech
3 rue du President Wilson
Levallois,
France
Email: remi.despres@free.fr
Roberta Maglione
Telecom Italia
Via Reiss Romoli 274
Torino 10148
Italy
Email: roberta.maglione@telecomitalia.it
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